1. Field of the Invention
The present invention generally relates to semiconductor devices and, more particularly, to a semiconductor device suitable for forming a three-dimensional structure in which a plurality of semiconductor devices are provided in a stacked state.
In association with reduction in size, weight and thickness of electronic apparatuses, reduction in size and thickness is required for semiconductor devices used in the electronic apparatuses. In order to satisfy such a requirement, a semiconductor package has been changed from a quadra-flat package to a ball grid array (BGA) package or chip size package (CSP).
A fan-out type package is popular among those packages. In the fan-out type package, a semiconductor chip is mounted on a redistribution substrate (generally referred to as an interposer) and external connection terminals are arranged around the semiconductor chip.
2. Description of the Related Art
FIG. 1 is a cross-sectional view of a conventional fan-out type semiconductor device. In FIG. 1, a semiconductor chip 3 is mounted on an interposer 1 that is formed of a polyimide substrate or a glass-epoxy substrate. The semiconductor chip 3 is encapsulated by a seal resin 2. The semiconductor chip 3 is fixed to the interposer 1 by a die-bonding material 6 in a face-up state in which a circuit forming surface of the semiconductor chip 3 faces upward. Bonding pads 5 and ball pads 8 are formed on the upper surface of the interposer 1, and the bonding pads 5 are connected to the respective ball pads 8 by wiring patterns.
Electrodes of the semiconductor chip 3 are connected to the respective bonding pads 5 by gold (Au) wires 4. The surface of the semiconductor chip 3 on which the semiconductor chip 3 is-mounted is encapsulated by the seal resin 2 such as epoxy resin so as to protect the semiconductor chip 3, the Au wires 4, the bonding pads 5 and the ball pads 8. Additionally, VIA holes 9 are formed in the interposer 1 at positions corresponding to the ball pads 8 so that the ball pads 5 are exposed in the VIA holes 9. Solder balls 7 are provided on the bonding pads 5 serving as bottoms of the VIA holes 9 opening on the lower surface of the interposer 1. Accordingly, the semiconductor chip 3 is electrically connected to the solder balls 7 serving as external connection terminals via the interposer 1. The solder balls 7 protrude from the lower surface of the interposer 1.
FIG. 2 is a cross-sectional view of a CSP type semiconductor device in which a semiconductor chip is mounted by a flip-chip mounting method. In FIG. 2, parts that are the same as the parts shown in FIG. 1 are given the same reference numerals, and descriptions thereof will be omitted.
In FIG. 2, the semiconductor chip 3 is mounted on the interposer 1 by a flip-chip mounting method in a face-down state in which the circuit forming surface of the semiconductor chip 3 faces the interposer 1. That is, the semiconductor chip 3 has a connection bumps 12, which are connected to the bonding pads 5. An under fill material 11 is filled between the semiconductor chip 3 and the interposer 1 so that the semiconductor chip 3 is fixed to the interposer 1 by the under fill material 11. Similar to the semiconductor device shown in FIG. 1, through holes (VIA holes) 9 are provided in the interposer 1, and the solder balls 7 protrude from the lower surface of the interposer 1.
In the above-mentioned semiconductor devices, the mounting area of the package including the semiconductor chip is reduced so that the package size is reduced to almost the size of the semiconductor chip. Accordingly, the reduction in the two-dimensional size of the package is considered to be almost the limit. Thus, the reduction in size of the semiconductor devices must be directed to the three-dimensional scheme. That is, in order to reduce the size of the semiconductor devices, consideration must be given on not only how to reduce a mounting area but also how to reduce a mounting volume.
It is a general object of the present invention to provide an improved and useful semiconductor device in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a semiconductor device which can directly connect to another semiconductor device in a stacked arrangement so that a plurality of the semiconductor devices can be mounted on a mounting board in a three-dimensional structure by stacking one on another.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a semiconductor device comprising: a first semiconductor element; a redistribution substrate having a first surface and a second surface opposite to the first surface, the first semiconductor element being mounted on the first surface; a plurality of electrode pads arranged on the first surface of the redistribution substrate, the electrode pads being electrically connected to the first semiconductor element; a plurality of protruding electrodes provided on the respective electrode pads; and a plurality of through holes extending from the second surface of the redistribution substrate to the respective electrode pads, wherein the first semiconductor element is encapsulated by a seal material, and a height of each of the protruding electrodes from the first surface is larger than a height of a sealed portion of the first semiconductor element from the second surface.
According to the above-mentioned invention, the through holes are formed in the redistribution substrate such as an interposer so that the back side of the electrode pads are exposed on the bottom of the respective through holes. Additionally, each of the protruding electrodes is higher than the sealed portion of the first semiconductor element, when two semiconductor devices are stacked one on another, the sealed portion of the upper semiconductor device can be accommodated in a space between the redistribution substrates of the upper and lower semiconductor devices while the protruding electrodes of the upper semiconductor device are bonded to the electrode pads of the lower semiconductor device through the through holes of the redistribution substrate of the lower semiconductor device. That is, the distance between the upper semiconductor device and the lower semiconductor device can be defined only by the protruding electrodes of the upper semiconductor device being bonded to the electrode pads of the lower semiconductor device. Thus, the stacked structure of the semiconductor devices can be achieved in a simple structure. Additionally, the electrode pads can be freely positioned around the first semiconductor element on the first surface of the redistribution substrate by forming wiring patterns on the first surface under the first semiconductor element.
Additionally, there is provided according to another aspect of the present invention a semiconductor device comprising: a first semiconductor element; a redistribution substrate having a first surface and a second surface opposite to the first surface, the first semiconductor element being mounted on the first surface; a plurality of electrode pads arranged on the first surface of the redistribution substrate, the electrode pads being electrically connected to the first semiconductor element; a plurality of through holes extending from the second surface of the redistribution substrate to the respective electrode pads; and a plurality of protruding electrodes formed on the respective electrode pads through the respective through holes, wherein the first semiconductor element is encapsulated by a seal material, and a height of each of the protruding electrodes from the second surface is larger than a height of a sealed portion of the first semiconductor element from the electrode pads.
According to the above-mentioned invention, the through holes are formed in the redistribution substrate such as an interposer so that the back side of the electrode pads are exposed on the bottom of the respective through holes and the protruding electrodes are formed on the respective electrode pads though the through holes. Additionally, since each of the protruding electrodes is higher than the sealed portion of the first semiconductor element, when two semiconductor devices are stacked one on another, the sealed portion of the lower semiconductor device can be accommodated in a space between the redistribution substrates of the upper and lower semiconductor devices while the protruding electrodes of the upper semiconductor device are bonded to the electrode pads of the lower semiconductor device. That is, the distance between the upper semiconductor device and the lower semiconductor device can be defined only by the protruding electrodes of the upper semiconductor device being bonded to the electrode pads of the lower semiconductor device. Thus, the stacked structure of the semiconductor devices can be achieved in a simple structure. Additionally, the electrode pads can be freely positioned around the first semiconductor element on the first surface of the redistribution substrate by forming wiring patterns on the first surface under the first semiconductor element.
Additionally, there is provided according to another aspect of the present invention a semiconductor device comprising: first and second semiconductor elements; a redistribution substrate having a first surface and a second surface opposite to the first surface, the first semiconductor element mounted on the first surface and the second semiconductor element mounted on the second surface; a plurality of first electrode pads arranged on the first surface of the redistribution substrate, the first electrode pads being electrically connected to the first semiconductor element; a plurality of second electrode pads arranged on the second surface of the redistribution substrate, the second electrode pads being electrically connected to the second semiconductor element; a plurality of via holes electrically connecting the first electrode pads to the respective second electrode pads; a plurality of protruding electrodes provided to the first electrode pads, wherein the first and second semiconductor elements are individually encapsulated by a seal material, and a height of each of the protruding electrodes from the first surface is larger than a height of a sealed portion of the first semiconductor element.
According to the above-mentioned invention, the semiconductor elements are mounted on both sides of the redistribution substrate, and also the electrode pads are formed on both sides of the redistribution substrate. The protruding electrodes are formed on the electrode pads on one side of the redistribution substrate, and the electrode pads on one side of the redistribution substrate are electrically connected to the respective electrode pads on the opposite side of the redistribution substrate. Accordingly, a semiconductor device having protruding electrodes each of which is higher than the sealed portion formed on the side where the electrode pads are not provided can be stacked on the semiconductor device according to the present invention from the side where the protruding electrodes are not provided. Thereby, a stacked structure of the semiconductor devices can be achieved in a simple structure.
Additionally, there is provided according to another aspect of the present invention a method for manufacturing a semiconductor device comprising first and second semiconductor elements and a redistribution substrate having a first surface and a second surface opposite to the first surface, the first semiconductor element mounted on the first surface and the second semiconductor element mounted on the second surface, the method comprising the steps of: mounting the first semiconductor device on the first surface of the redistribution substrate; placing the redistribution substrate on a jig after turning over the redistribution substrate, the jig having a depression in which the first semiconductor element is accommodated, the jig also having a buffer member supporting the first semiconductor element in the depression; and mounting the second semiconductor element on the second surface of the redistribution substrate.
According to the above-mentioned invention, when mounting semiconductor elements on both sides of the redistribution substrate after one of the semiconductor elements is mounted on one side of the redistribution substrate, the other one of the semiconductor elements can be mounted while the one of the semiconductor elements is supported from underneath. Accordingly, the semiconductor elements can be positively mounted on both sides of the redistribution substrate.
Additionally, there is provided according to another aspect of the present invention a method for stacking a plurality of semiconductor devices each of which comprises: a redistribution substrate; a semiconductor element mounted on the redistribution substrate and protected by a package; a plurality of protruding electrodes arranged on the redistribution substrate; and a plurality of electrode pads provided on a surface opposite to a surface on which the protruding electrodes are provided so that the electrode pads are opposite to the respective protruding electrodes, wherein the semiconductor devices are stacked by connecting the protruding electrodes of one of the semiconductor devices to the electrode pads of one of the semiconductor devices located on an upper side, the method comprising the steps of: placing each semiconductor device so that the protruding electrodes face upward; and applying flux to the protruding electrodes by using a transfer head carrying the flux in a shape corresponding to an arrangement of the protruding electrodes so that the flux is applied only to the protruding electrodes.
According to the above-mentioned invention, the flux is applied to the protruding electrodes by the transfer head. Since the transfer head has the flux applying part having a configuration corresponding to an area where the protruding electrode are arranged, an appropriate amount of the flux can be applied only to the protruding electrodes. Thereby, the adjacent protruding electrodes and the adjacent electrode pads can be prevented from being short circuited when a reflow process is performed.
Additionally, there is provided according to another aspect of the present invention a method for stacking a plurality of semiconductor devices each of which comprises: a redistribution substrate; a semiconductor element mounted on the redistribution substrate and protected by a package; a plurality of protruding electrodes on the redistribution substrate; and a plurality of electrode pads provided on a surface opposite to a surface on which the protruding electrodes are provided so that the electrode pads are opposite to the respective protruding electrodes, wherein the semiconductor devices are stacked by connecting the protruding electrodes of one of the semiconductor devices to the electrode pads of one of the semiconductor devices located on an upper side, the method comprising the steps of: conveying each semiconductor device to a flux applying position at which a flux applying member is located in a state in which the protruding electrodes of the semiconductor device face downward, the flux applying member having a flux filling part corresponding to an area in which the protruding electrodes are arranged; and applying flux to the protruding electrodes by putting the protruding electrodes into the flux filled in the flux filling part.
According to the above-mentioned invention, the protruding electrodes are put into the flux filled in the flux filling part having a configuration corresponding to an area where the protruding electrodes are arranged. Accordingly, an appropriate amount of the flux can be applied only to the protruding electrodes. Thus, the adjacent protruding electrodes and the adjacent electrode pads can be prevented from being short circuited when a reflow process is performed. Additionally, the semiconductor device is stored, after being manufactured, in a state in which the protruding electrodes face downward, there is no need to turn over the semiconductor device, thereby simplifying the process of applying the flux to the protruding electrodes.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.